This invention relates generally to apparatus for entangling of multi-filament yarns, and more particularly concerns air jets and feed mechanisms which entangle multi-filament yarns at high speed, at reduced air pressure and air flow, and with consistently spaced tacks and blooms.
It is well known in the textile industry that continuous filament yarn bundles produced from a spinnerette have zero twist and perform poorly in many of the common textile operations such as winding, weaving, knitting, and the like. The poor performance is primarily due to the looseness of the structure that permits individual filaments to snap and break thus forming fluff balls, slubs, ringers, wraps, strip backs, or similar defects. Zero twist yarns also have a tendency to run in the form of a ribbon over guides, rollers and so forth whereby as a result of increased frictional contact, the yarns are more readily abraded and subject to breakage. As a result of these shortcomings, continuous filament producers usually carry out the additional step of twisting such continuous multi-filament yarn bundles to provide an acceptable starting product for fabric weaving, knitting, and carpet tufting. The twisting operation serves to compact and unify the yarn bundle thus resulting in a more cohesive structure which resists the pulling out of the individual filaments. The twisting operation, however, is expensive and time consuming and does not lend itself to continuous operation which characterizes much of the manufacturing process in the preparation of zero twist continuous multi-filament yarn bundles.
It is also well known in the textile industry that a multi-filament yarn bundle can be crimped by setting the yarn in a distorted configuration. Mechanical crimping, when used to achieve the distorted configuration, is time consuming and usually has limited processing speeds. Such mechanical crimping may also adversely affect the physical properties of the yarn.
In order to overcome the expense of a twisting operation, it is well known in the art to employ air jets to interlace and entangle the yarn to increase its bulk and to consolidate and unify the multi-filament yarn.
Early work regarding air entangling was directed primarily to consolidating and unifying the yarn bundle in order to impart integrity to the yarn bundle. In that regard, Bunting, et al., U.S. Pat. No. 3,110,151, discloses a number of different entangling jet configurations in which air is introduced into an entangling chamber while the yarn is continuously drawn through the entangling chamber. The jets and processes disclosed in the Bunting, et al. patents are specifically designed to interlace (called maypoling). The resulting yarn has periodic variations in the yarn structure but those variations are not observable with the unaided eye and are only observable with the aid of a microscope. Because the interlacing process in the Bunting, et al patent is carried out under positive tension with no mechanical overfeed, there is no tendency on the part of the yarn to bulk as a result of the action of the air jet. In addition, because bulking is not apparently an objective, the Bunting, et al. patent discloses consolidating light weight nylon yarns of 55 denier/17 filaments at speeds of 5000 yards per minute (yd./min.) using air at a pressure of 100 pounds per square inch gauge (psig.). Alternatively, heavier cellulose acetate yarns of 300 denier/80 filaments were run at only 100 yd./min. at an air pressure of 75 psig.
Fletcher, et al., U.S. Pat. No. 3,389,444 (and related U.S. Pat. Nos. 3,286,321 and 3,220,082) discloses various air jets for entangling yarns. Particularly, the Fletcher patent discloses processing zero twist yarns so that the yarn is relatively free of any loops or other noticable discontinuities. One jet disclosed in the Fletcher, et al. patent (FIG. 7) has diametrically opposed tapered air orifices on either side of the entangling chamber. The diametrically opposed air orifices are of equal size and are connected to a source of pressurized air by means of an annular chamber around the entangling chamber which results from inserting the cylindrical air jet into a bore at right angles to an intersecting bore. The resulting annular chamber is not cylindrical in shape (ring shape) but instead is half moon shaped on the sides of the bore connected to the air supply. Fletcher et al. also teaches polishing the surfaces of the entangling chamber to increase the closeness (periodic spacing) of the tacks. By using such an air jet, cellulose acetate yarn of 220 denier/15 filament is purportedly entangled at 714 meters per minute (m./min.) at air pressure of 66 psig (col. 8, lines 11-19, 47-66). The yarn however, had a loopy appearance with spots of extremely tight filament interweaving alternating with randomly occurring arch shaped loops. The yarn when woven into fabric had the appearance of containing staple yarn of poor uniformity plus some of the general effect of a skip dent type weave.
In order to provide yarn that is suitable for tufting into carpets, it is necessary to not only consolidate and unify the filaments in the yarn but to impart bulk to the yarn as well. In that regard, Whitted, et al. U.S. Pat. Nos. 4,223,520 and 4,064,686 disclose air entangling jets in which the air jets have two diametrically opposed equal diameter air orifices. In addition, the entangling chamber has a restricted outlet. Entangling is carried out by overfeeding the yarn into the entangling chamber at an overfeed rate of approximately 11/2 to 2%. The air jets purportedly can entangle yarn of unspecified size at speeds of up to 2500 feet per minute (833 yd./min.) using air pressure between 80 and 180 psig. Commercial machines purportedly using the Whitted technology run carpet yarns of 1,000 to 2,000 denier at speeds of about 250-400 yds./min. and at pressures over 180 psig. The resulting yarn has alternate areas of high bulk (blooms) and compacted tacks.
Sheehan, et al. U.S. Pat. No. Re. 31,376 also discloses a yarn having alternating blooms and tacks. Sheehan, et al. does not disclose the particular air jet used but states that improved results are achieved by increasing the air pressure to between 100 and 200 psig and feeding the yarn of unspecified size under tension amounting to about a 2% underfeed.
Whitener U.S. Pat. No. 4,570,312 discloses a feed apparatus for an air entangling system to produce yarn having high bulk (blooms) and intervening compacted tacks by means of a double roll godet. Apparently because the yarn is wrapped on the godet before entering the air jet and after exiting the air jet, the pulsating tension created by the air jet causes the godet to alternatively speed up and slow down the feed of the yarn to the air jet to accommodate the bulking and tacking of the yarn. Such machines purportedly can run in speeds in excess of 1100 m./min. on yarns of unspecified size, but there is no disclosure of the air pressure required at that speed. It is believed that commercial machines using that arrangement for entangling carpet yarn of 1,000-2,000 denier will run at about 800-900 m./min. at air pressures in excess of 200 psig.